Thermoelectric apparatus



Oct. 19, 1965 Filed Des. 2e, 1962 4 Sheets-Sheet 1 SEA WATER l/VPU7'Law/,vf mediare-'0 1N V EN TOR.

py J. Solamengf/f.

ATTORNEY Oct. 19, 1965 H. s. soMMERs. JR

THERMOELECTRIC APPARATUS 4 Sheets-Sheet 2 Filed Dec. 26, 1962 Oct. 19,1965 H. s. soMMERs. JR 3,212,272

THERMOELECTRIC APPARATUS I N V EN TOR. 01113/ J'. J' 011m ergJ ATTORNEYOf. 19, 1965 H. s. SQMMERS. JR 3,212,272

THERMOELECTRIC APPARATUS Filed Dec. 26, 1962 4 Sheets-Sheet 4 Z; 7 if ZX14 if@ S54 v p x M75/7 5 b /A/P//r- United States Patent() 3,212,272THERMGELECTRIC APPARATUS Henry S. Sommers, r., Princeton, NJ., assignerto Radio Corporation of America, a corporation of Delaware @riginalapplication July 30, 1957, Ser. No. 675,211.

Divided and this application Dec. 26, 1962, Ser. No.

8 Claims. (Cl. 62-3) The present invention relates to thermoelectricapparatos, and more particularly to systems for effecting a change ofstate of material using thermoelectric heat pumps. This application is adivision of an application tiled by Henry S. Sommers, Jr., Serial No.675,211, on Iuly 30, 1957 for Thermoelectric Apparatus.

Thermoelectric heat pumps of the type suitable for use in systemsprovided by the present invention operate in accordance with the Peltiereffect. Basically, such heat pumps include a body of material having ahigh thermoelectric power, such as a semiconductor, bonded between apair of metal electrodes. When current passes through the heat pump, oneof the electrodes provides a cold junction which absorbs heat from theambient, while the other electrode provides a hot junction whichreleases heat to the ambient. In this Way, heat is pumped through thethermoelectric heat pump from one junction to the other and atemperature gradient is established thereacross. An amount of energy isexpended in pumping heat to a higher temperature across the temperaturegradient. In accordance with the invention, a thermoelectric heat pumpis utilized with optimum efficiency upon minimization of the temperaturegradient. The invention is described herein as applied in a novel systemfor effecting a change of state or physical phase in a material which isliquid at normal, ambient temperatures, and in particular to systems forthe distillation of water by a cyclic change of state process.

The availability of a huge supply of pure water is essential to modernhuman existence. The largest and most accessible supply of water residesin the sea. However, the saline content of sea Water is too high to makeit suitable for human consumption. It has been proposed heretofore todistill sea Water, thereby providing an almost inexhaustible supply offresh water. Such proposals have not been extensively accepted, due totheir being economically unfeasi'ble. Prior apparatus for diS- tillingsea water has been dicult to construct, extremely complex, orexcessively bulky. Due to the novel incorporation of thermoelectric heatpumps, a system provided by the present invention may be smaller,simpler, and less expensive to operate than those heretofore proposed.

Briey described, the invention involves the use, in a system foreffecting `a change of state, of a unit wherein changes of statecyclically take place. The unit may comprise a structure which isinternally compartmentalized by thermoelectric heat pumps. A differentcompartment is provided on opposite sides of each of the heat pumps. Inone of the compartments, a change of state or phase of one type iseffected while a change of state or phase of the type opposite theretotak-es place simultaneously in the other compartment. For example, watermay be evaporated or frozen in the one compartment and, respectively,condensed or melted in the other compartment. The thermoelectric heatpumps are structurally adapted to obtain maximum heat pumping efficiencyby virtue of the disposition of the compartments in which the changes ofstate are effected in minimizing the temperature drop across each of theheat pumps.

It is therefore an object of the present invention to 3,212,272 PatentedOct. 19, 1965 "ice provide more efciently operating thermoelectricAapparatus.

It is a further object of the present invention to provide improvedsystems for cyclically effecting changes of state or phase which aresuitable for use in purifying liquid mediums.

It is a still further object of the present invention to provideimproved systems for effecting changes in state which incorporate, in anovel manner, improved thermoelectric apparatus.

It is a still further object of the present invention to provide systemsfor effecting changes of `state which may be simpler, less complex,smaller in size, and which have lower operating costs than such systemswhich have been heretofore available.

Other objects and advantages of the present invention will, of course,become apparent and immediately suggest themselves to those skilled inthe art to which the invention is directed from a reading of thefollowing description in connection with the `accompanying drawings inwhich:

FIG. 1 is a ilow chart showing the operation of a system incorporatingthe invention;

FIG. 2 is a fragmentary, sectional view of one form of thermoelectricfreezing-melting unit suitable for use in the system illustrated in FIG.1, the section being taken along the line 2 2 of FIG. 3;

FIG. 3 is a sectional View taken along the line 3 3 of FIG. 2;

FIG. 4 is a sectional View taken along the line 4 4 of FIG. 2;

FIG. 5 is a simplified, schematic diagram showing the electricalconnection of the thermoelectric freezing-melting unit illustrated inFIGS. 2, 3 and 4;

FIG. 6 is a sectional view of another embodiment of a thermoelectricfreezing-melting unit constructed in accordance with the presentinvention and useful in the system illustrated in FIG. 1, the sectionbeing taken along line 6 6 of FIG. 7; land FIG. 7 is a sectional viewtaken along the line 7 7 of FIG. 6 as viewed in the direction of thearrows.

Referring more particularly to the drawings, purification of sea Wateris effected in the system shown in FIG. 1 by means of freezing and then.melting the sea water in accordance with a cyclic process. The yseaWater is initially passed through a heat exchanger 16, wherein it isprecooled.v After leaving the heat exchanger, the sea water isintroduced into a thermoelectric freezingmelting unit 18. The unit 18 isdescribed in detail hereinafter. Brieiiy, it incorporates a novel.structure including thermoelectric heat pumps for cyclically freezingthe sea watei into ice and thereafter melting the ice to provide freshWater. Since the freezing and melting operation takes place at atemperature of approximately 32 degrees Fahrenheit, which is normallybelow the ambient temperature, a refrigeration unit 20, which may -be ofany conventional type, is used to cool a chamber 22 in which thethermoelectric freezing-melting unit is located. The chamber 22 may bean insulated box Vand is illustrated in FIG. 1 by dash lines. A directcurrent power supply 24, for example of known design, is used to provideoperating power for the thermoelectric heat pumps in the thermoelectricfreezing and melting unit 18. Both fresh water and brine are produced inthe thermoelectric freezing-melting unit. The fresh Water and the brinepass through the heat exchanger 16 so as to precool the input sea Water.The brine is rejected, as by being pumped back into the sea, and thefresh water is available for consumption.

One form of thermoelectric freezing-melting unit which can be used inthe system shown in FIG. 1 is structurally illustrated in FIGS. 2, 3 and4. The unit is enclosed in a container 116 which may be made frominsulating, refractory material such as ceramic material. The sea wateris fed into a manifold 118. The manifold 118 is connected by way ofconduits 120 into the container 116. Valves 122, which are schematicallyillustrated as incorporating a flap-operated mechanism, control the owof sea water from the conduits 120 into the container 116. A pluralityof thermoelectric heat pump panel units 124,126, 128 and 129 aredisposed on an inclined plate 130. The plate 130 is supported on astanchion plate 132 and at a side wall of the container 116. Theinclined plate 130 may be composed of insulating refractory material andhas a plurality of rows of apertures 168 therein. The portions of theplate 130 around the apertures 168 provide seats for flap valves 170.

Each of the heat pump panel units 124, 126, 128 and 129 is provided by aplurality of thermocouple elements 136, 138, 140, 142 and 144. Theseelements are each in the shape of a parallelepiped. A body ofthermoelectrically active material 148,-such as a semi-conductor, issandwiched between a pair of conductive junction plates 150 and 152 toprovide each of the thermoelectric elements 136, 138, 140, 142 and 144.The junction plates 150 and 152 are connected, to adjacent junctionplates to provide the panel array of thermocouple elements for each ofthe heat pump panel units 124, 126, 128 and 129. Connector plates 184 ofinsulating material, such as a structurally strong, laminated,thermosetting plastic, are fastened to each adjacent junction plate 150and 152. A bar of insulating material 154 is attached at the top of eachof the heat pump units 124, 126, 128 and 129.

The heat pump units 124, 126, 128 and 129 define a plurality ofcompartments in the container 116. Adjacent ones of these compartmentsare freezing compartments and melting compartments, respectively. Duringone phase of the cycle of operation of the freezing-melting unit, thecompartments 156, 158 and 160 function as freezing compartments, whilethe other compartments 162 and 164 function as melting compartments. Thefreezing-melting unit 18 is illustrated in the drawings when operatingat an interval during one phase of the cycle of operation. However,during the next phase of the cyclical operation of the freezing-meltingunit 18, the compartments reverse in function. The compartments 156, 158and 160 then operate as melting compartments, and the compartments 162and 164 operate as freezing compartments.

The region between the bottom of the inclined plate 130 and the bottomof the container 116 provides a reservoir for fresh water. An oulet pipe172 is connected to the reservoir to extract the fresh water therefrom.In front of the thermoelectric heat pump panel units 124, 126, 128 and129 (to the left in FIG. 3 and FIG. 4), and between the side walls ofthe compartment 116, there is disposed a region or reservoir 174 for thecollection of concentrated sea water or brine. This brine ows throughthe compartments formed by the heat pump units into the reservoir 174.The brine from this reservoir is discharged through a pipe 176. A valve178, illustratively shown `as a flap valve, closes the brine reservoir174 during selected lperiods -of operation of the device. As shown inFIGS. 3 and 4, `a vertically disposed plate 180, which may beconstructed of insulating material, is attached between the end of eachof the heat pump panel units 124, 126, 128 and 129 and the left sidewall of the container 116 and guides the ow of the sea water and brinefrom each compartment into the brine reservoir 174.

In operation, the freezing-melting unit which is contained in thecontainer 116 is maintained at approximately the freezing point ofwater, namely zero degrees centigrade, by means of an auxiliaryrefrigeration unit,

as shown in FIG. 1. The sea water is permitted to flow into thealternate compartments 156, 158 and 160 by opening certain of the valves122 at the terminals of the corresponding conduits 120. The valves 170close the apertures 168 at the bottom of these compartments 156, 158 and160 as shown in FIG. 4. The valves leading into the brine dischargereservoir 174 from each of the compartments 156, 158 `and 160 aremaintained open, as also shown in FIG. 4. Sea water tlows through eachof the compartments 156, 158 and 160. The heat pump units 124, 126 and128 and 129 are operated, in a manner to be described in detailhereinafter in connection with FIG. 5, so that layers of fresh water iceform in each of the compartments 156, 158 and 160. Since, when saltwater freezes, the salt content tends to remain in the liquid, the iceformed in each of the containers 156, 158 and 160 will lbe essentiallysalt free. The more concentrated sea water passes into the brinereservoir 174 and is discharged through the pipe 176. Formation ofprogressively higher layers of ice in each of the compartments 156, 158and 160 is provided by energizing different ones of the thermocoupleelements 136, 138, 140, 142 and 144 in the heat pumps 124, 126, 128 and129 at different times. For example, the lowest one of the thermocoupleelements is energized first and until a layer of ice forms in theadjacent region of the compartments 156, 158 and 160 and growssutliciently to ll this region of the compartment with ice. Then, thenext higher thermocouple element is energized so that the ice grows -toalso lill this region of the compartments 156, 158 and 160. Byprogressively raising the position of the interface at which iceformation occurs, it is possible to fill the compartments entirely withfresh water ice. In the past, freezing-melting methods of distillationhave not proven successful, since a considerable amount -of sea wateroccluded to the small ice crystals which were formed. By controlledfreezing of sea water, in accordance with the invention, it is possibleto provide pure ice. This ice is subsequently melted to provide freshwater.

When the compartments 156, 158 and 160 are completely full of ice, thecycle is reversed. The junction plates 152 and 150 of the heat pumps124, 126, 128 and 129, which were arranged to be cold junctions forfreezing purposes, are reversed in their operation to become hotjunctions so as to melt the ice. The cyclic process may be continual.

A stage in the process is shown in FIGS. 2, 3 and 4. At this stage, thecompartments 156, 158 and 160 are functioning as freezing compartments,while the compartments 162 and 164 operate as melting compartments. Itmay be observed that projections 182 extend from the junction plates and152 into the compartments to prevent the ice formed therein fromslipping downwardly.

Sea water is permitted to flow through the valves 122 into thecompartments 156, 158 and 160. The valves 122 which lead to the othercompartments 162 and 164 are closed. Correspondingly, the valves at thebottom of the compartments 162 and 164 are open for the passage ofmelting ice water therethrough, whereas the valves 170 at the bottom ofthe compartments 156, 158 and 160 are closed to prevent the water fromflowing therethrough while ice is forming .in these compartments. Thebrine discharge valves 178 are open in the ice forming compartments 156,158 and 160 for the discharge of brine therefrom, whereas these valvesare closed in the melting compartments to prevent any melting freshwater from escaping into the brine discharge reservoir 174. Iceprogressively grows upwardly in the ice forming compartments 156, 158and 160. The interface between the sea water and the ice risesgradually. In the melting compartments, ice has been formed and ismelting from the bottom interface. This melting ice passes as ice water,through the apertures 168 on the bottom of the respective compattments,into the fresh water output reservoir and thence out of the fresh wateroutput pipe 172. As was mentioned heretofore, only one thermocoupleelement at a time is energized in each of the heat pump panels 124, 126,128 and 129. This element is the element adjacent to the interface.Freezing the ice Water at one level as the Water flows over theinterface permits the formation of pure ice without excessive occlusionof salt therein. The small temperature gradient between the adjacentcompartments and across each heat pump unit 124, 126, 128 and 129provides for greater efficiency of operation. Moreover, heat absorbedfrom the freezing water is efficiently pumped for use in melting thefresh Water ice in the adjacent compartment.

Referring now to FIG. 5, circuitry for cyclically changing the operationof the freezing-melting unit 18 is shown. Only three heat pumps areshown for purposes of simpliiied illustration. They are designated bythe reference numerals 186, 188 and 190. Each of the heat pumps isprovided by a plurality of thermocouple elements 192, 194, 196 and 198and 200. The junction plates of each of the thermocouple elements areconnected to the terminals of a pair of rotary switches 206 and 210.These switches are simultaneously actuated, as by a timing device 211,such as includes a clock motor. A direct-current power supply 202 isconnected to the rotating arms 204 and 208 of the switches 206 and 210.The positive terminal of the direct-current power supply is connected tothe arm 204 of one switch 206. The negative terminal of thedirect-current power supply 202 may be connected to the rotating arm 208of the other switch 210. In the position of the switches illustrated,the thermocouple element 194 of each of the heat pump units 186, 188 and190 is energized. It is assumed that the ice-Water interface,illustrated by the dash line 212, is disposed adjacent to the junctionplates of the energized thermocouple element 194. As the switchprogresses, successively higher ones of the thermocouple elements 196,198 and 200 are activated. After the thermocouple element 200 isactivated, the lowest one of the thermoelectric elements 192 is againactivated. However, this thermocouple element 192 is now activated inthe opposite sense, so that its junctions are reversed. The operation ofthe unit may be cyclical and continual. It will be observed that thechange from the melting cycle to the freezing cycle results from thereversal of the direction of current flow. Connected to the switches 206and 210 and the power supply 202 may be a number of solenoids 214 foroperating the valves in the sequence above set forth.

There has therefore been described a unique system for purifying seawater to provide fresh water therefrom. The system is, as may beobserved, much less complicated than systems for this purpose which wereheretofore available. The principle of operation involved may be used inother systems for effecting a change of phase by use of thermoelectricheat pump apparatus. For example, by a rearrangement of the switchingand valve sequence, a series of molten and solid zones can be made topass upwardly through each cell, thus making the unit into aregenerative zone purifier. This will permit the adaptation of the highthermal eiciency of the thermoelectric heat pump to the zonepurification of materials.

Another embodiment of a freezing-melting unit provided by the presentinvention is illustrated in FIGS. 6 and 7. A container 220 of insulatingmaterial, for example, some refractory insulating material such as aceramic, includes a number of heat pump units 222, 224, 226 and 228which are arranged vertically and supported on I beams 230, 232, 234 and236, respectively. These beams may be constructed from the same materialas the container 220. Each of the heat pumps consists of a plurality ofthermocouple elements 238, 240, 242, only three of which are shown forpurposes of simplifying the illustration. Each element is in the form ofa tapered bar of some thermoelectrically active material. Metal plates244 are in conductive contact with the side surfaces of the 6 bars ofthermelectrically active material. Tapered cells are formed between thethermoelectric elements of adjacent heat pump units at each level of therespective thermocouple elements. The nar-row extremity of these cellsis disposed at the bottom thereof. The bottom-most thermoelectricelement rests on a bar 246 of insulating material, the respective bars246 resting upon the I beams 230, 232, 234 and 236. A vertical bar 250of insulating material is disposed between the front of each of thethermoelectric heat pump units and a front wall 252 of the container220. Bars 254 of insulating material, which are tapered, separate eachof the thermoelectric elements 238, 240, 242. Other bars 256 `ofinsulating material are disposed on the tops of the upper thermocoupleelements 238.

A sea water input manifold 260 is connected through a series of pipes262 into the container 220. A different pipe leads into each group ofthe cells formed at the various thermocouple element levels between theadjacent thermocouple elements and between the end thermocouple elementsand the end walls 264 of the container 220. Flap valves similar to thevalves 122 used in FIG. 2 control the flow of sea water from therespective pipes 262 into the various cells.

The iloor 266 of the container 220 is sloped gently (as seen in FIG. 6),and conduits 268 leading from the container 220 are disposed at thelower-most level of the floor 266. A conduit 26S is connected at thebottom of the container in each `of a plurality of fluid collectionchambers 270 formed by the surfaces of the I beams 230, 232, 234 and236. A two-way distribution valve 272 is connected to each of theconduits 268 for channeling the fluid collected in the chambers 270 toeither one of a fresh water output conduit 274 or a brine dischargeconduit 276.

In operation, the heat pumps 222, 224, 226 and 228 are activated, as bybeing connected in parallel to a cornmon source of direct current. Thecurrent through each of the thermocouple elements 238, 240 and 242 ispolarized so that adjacent ones of the metal plates 244 which form thejunctions of the thermocouple elements 238, 240 and 242 provide eitherhot (heat discharging) junctions or cold (heat absorbing) junctions.Freezing and melting of fresh water ice occurs simultaneously inalternates ones of the cells. The valves coupled to the pipes 262 admitsalt Water into the cells between alternate pairs of adjacent pumps 222,224, 226 and 228. Thus, the cells between pairs of adjacent heat pumps222, 224 and heat pumps 226, 228 are cells in which freezing takesplace. The valves leading into these cells are open, as indicated in thedrawing, and sea water enters therein. Because of the taperedconstruction of the cells, freezing will start in the constricted bottomthereof and the ice-salt Water interface will rise in each of the cellsuntil all of the cells are filled with pure ice.

The thermocouple elements 238, 240 and 242 are tilted downwardly fromthe sea water input side of the container 220 to the front side 252thereof, as seen in FIG. 6. Thus, the salt water will flow down in eachcompartment, through the duct formed by adjacent ones of the verticalbars 250, and through the openings 278 near the front end of each of theI beams 230, 232, 234 and 236. This overflow sea water, which is notfrozen, will be more concentrated since some fresh water is extractedtherefrom to form ice in the cells and the overflow sea water may beconsidered to be brine. This brine will collect in the chambers 270formed between the I beams 230 and 232 and between the I beams 234 and236 and will be withdrawn through the conduits 268 thereof. Thedistributing valve 272 is adjusted so that this brine iloWs through thebrine discharge conduit 276. At the same time, ice which has alreadybeen formed in the cells between other heat pump units, as between theunits 224 and 226, will be melted by the hot junction plates 244 of thethermocouple elements 238, 240 and 242. The valve leading into thesecells between the heat pump units 224 land 226 are closed at this timeso that salt water cannot enter them. The fresh water ice in the meltingcells melts at both the top and bottom and flows downwardly along theinclined surfaces of the ice into the chambers 270 between the I beammembers 232 and 234. Also, the water from the melted ice in the upperones of the cells falls into the cells immediately beneath and assistsin melting the ice contained in the lower cells. The ice melts first atthe heated walls of the thermocouple elements, and the tapered blocks ofice will gradually settle. Because of the settling of the ice in thecells, a final segment of ice will be left in the constricted bottoms ofeach of the cells at the end of a melting cycle. These segments of icewill serve as seeds to facilitate the growth of fresh water ice in thefreezing part of the cycle, thus assuring the proper growth of pure ice,free from salt occlusions.

The process is cyclical so that freezing and melting occurs successivelyin the same cells. Some advantages of the embodiment of the inventionillustrated in FIGS. 6 and 7 are that all of the thermocouple elements238, 240 and 242 in all of the heat pump units 222, 224, 226 and 228-operate simultaneously. In other words, the duty cycle of the equipmentis 100 percent. The thermal efficiency of the apparatus is alsoincreased since melting occurs directly at the walls of the thermocoupleelements, that is, at the metal junction plates 244. The melting occursfirst at the heated metal plates 244 and the ice settles as it melts atthe surface thereof. Because of the constricted ends of the cells, themaintenance of a seed of pure water ice is possible to facilitate thegrowth of pure ice during the freezing cycle.

What is claimed is:

1. In a system for purifying a tuid medium, the combination comprising aplurality of thermoelectric heat pump units having hot and coldjunctions on opposite sides thereof, at least one of said heat pumpunits being disposed with the hot junction side thereof opposite the hotjunction side of one of said heat pump units adjacent thereto and withthe cold junction side thereof opposite the cold junction side of`another of said heat pump units adjacent thereto so as to define a pairof compartments on opposite sides thereof, means for passing said fluidmedium through the one of said compartments defined by said coldjunction sides for progressively freezing said iiuid medium to purifysaid medium, the heat developed in the one of said compartments formedby said hot junction sides being adapted to melt previously frozen,purified bodies of said uid medium disposed therein, and means forselectively withdrawing said puriiied fluid medium from saidcompartments in the fluid state.

2. In a system for purifying a fluid medium, the combination comprisinga plurality of thermoelectric heat pump units having hot and coldjunctions on opposite sides thereof, at least one of said heat pumpunits being disposed with the hot junction side thereof disposed ppositethe hot junction side' of one of saidy heat pump units adjacent theretoand with the cold junction side thereof opposite the cold junction sideof another of said heat pump units adjacent thereto so as to define apair of compartments on opposite sides thereof, a container for housingsaid heat pump units, said container including at least one inclinedplate for supporting said heat pump units with said compartmentsvertically disposed above said plate, said plate and the bottom wall ofsaid container cooperating to deiine a reservoir therebetween, valvemeans in said inclined plate at the bottom of each of said compartmentsfor selectively withdrawing therefrom into said reservoir iuid which hasbeen purified, other valve means in said container for selectivelyadmitting into said compartments said fluid medium to be purified sothat said uid medium flows in a direction downwardly along said inclinedplate, means communicating with said container for withdraw ing saidfluid medium admitted therein by said other valve means, said last-namedmeans being disposed near the lower end of said inclined plate, andmeans for controlling said valve means for opening those of saidiirstnamed valve means leading to those of said compartments defined bysaid hot junction sides and for opening those of said other valve meansfor admitting fluid into those of said compartments defined by said coldjunction sides.

3. In a system for purifying a fiuid medium, the combination comprisinga plurality of thermoelectric heat pump units having hot and coldjunctions on opposite sides thereof, at least one of said heat pumpunits being disposed with the hot junction side thereof opposite the hotjunction side of one -of said heat pump units adjacent thereto and withthe cold junction side thereof opposite the cold junction side ofanother of said heat pump units adjacent thereto so as to deiine a pairof compartments on opposite sides thereof, each of said heat pump unitscomprising a plurality of thermocouple elements, each of said elementsbeing provided by a body of thermoelectrically active material disposedbetween conductive junction members, said elements being disposed withsaid junction members aligned to form said hot and cold junction sidesof said heat pump units, and means for energizing said thermocoupleelements by passing direct current therethrough, said energizing meansbeing operative to cyclically change the direction of iiow of saiddirect current.

4. In a system for purifying a fluid medium, the combination comprisinga plurality of thermoelectric heat pump units having hot and coldjunctions on opposite sides thereof, at least one of said heat pumpunits being disposed with the hot junction side thereof opposite the hotjunction side of one of said heat pump units adjacent thereto and withthe cold junction side thereof opposite the cold junction side ofanother of said heat pump units adjacent thereto so as to define a pairof compartments on opposite sides thereof, each of said units comprisinga plurality of thermocouple elements, each of said elements beingprovided by a body of thermoelectric material and conductive members onopposite surfaces of said body, said elements being aligned with eachother in a column extending between the ends of said compartments, anddirect current power supply means for energizing individual ones of saidthermocouple elements in each of said heat pumps in sequence, theelements adjacent one of the ends of each of said compartments beinginitially energized, and all of said elements being energized insequence for predetermined intervals.

5. The invention as claimed in claim 4 including means for cyclicallyreversing the polarity of the direct current from said supply meansadapted to ow through each of said elements, a cycle being completedwhen all of said elements in said columns which comprise said heat pumpsare energized in said sequence.

6. In a system for purifying a fluid medium, the comblnatlon comprisinga plurality of thermoelectric heat p'ump units having hot and coldjunctions on opposite sides thereof, at least one of said heat pumpunits being disposed with the hot junction side thereof opposite the hotjunction of one of said heat pump units adjacent thereof and with thecold junction side thereof opposite the cold junction side of another ofsaid heat pump units adjacent thereto so as to define a pair ofcompartments on opposite sides thereof, each of said heat pump unitscomprising a plurality of thermocouple elements provided by taperedbodies of thermoelectrically active material having conductive memberson opposite sides thereof, said elements being disposed in a column withadjacent ones of said bodies in said column having the wide and narrowends adjacent each other, and the Wide ends of said bodies beingdisposed below the narrow ends thereof in said column, whereby each ofsaid compartments is divided into a plurality of tapered cellscommunicating with each other.

7. The invention as recited in claim 6 including direct current powersupply means for energizing all of said thermocouple elementssimultaneously, and means for cyclically reversing the direction ofcurrent ow from said power supply means through each `of said elements.

8. In a system for purifying a fluid medium, the combination comprisinga plurality of thermoelectric heat pump units providing heated andcooled surfaces on opposite sides thereof, means for mounting said heatpump units with said cooled and said heated surfaces of different onesthereof opposed to form compartments therebetween, means for selectivelyadmitting said medium to be puried into said compartments, means forselectively withdrawing said medium from said compartments in the fluidstate, and means for controlling said last two named means for admittingonly into the ones of said compartments formed by said cooled surfacessaid iluid medium to be purified and for withdrawing said Huid in theuid state after purification thereof only from the ones of saidcompartments formed by said heated surfaces.

References Cited by the Examiner UNITED STATES PATENTS 706,511 8/02Barrath 62348 2,542,892 2/51 Bayston 62-348 2,575,892 11/51 R-oberts62-348 2,779,172 l/ 5 7 Lindenblad 62--3 NORMAN YUDKOFF, PrimaryExaminer.

1. IN A SYSTEM FOR PURIFYING A FLUID MEDIUM, THE COMBINATION COMPRISINGA PLURALITY OF THERMOELECTRIC HEAT SIDES THEREOF, AT LEAST ONE OF SAIDHEAT PUMP UNITS BEING DISPOSED WITH THE HOT JUNCTION SIDE THEREOFOPPOSITE THE HOT JUNCTION SIDE OF ONE OF SAID HEAT PUMP UNITS ADJACENTTHERETO AND WITH THE COLD JUNCTION SIDE THEREOF OPPOSITE THE COLDJUNCTION SIDE OF ANOTHER OF SAID HEAT PUMP UNITS ADJACENT THERETO SO ASTO DEFINE A PAIR OF COMPARTMENTS ON OPPOSITE SIDES THEREOF, MEANS FORPASSING SAID FLUID MEDIUM THROUGH THE ONE OF SAID COMPARTMENTS DEFINEDBY SAID COLD JUNCTION SIDES FOR PROGRESSIVELY FREEZING SAID FLUID MEDIUMTO PURIFY SAID MEDIUM, THE HEAT DEVELOPED IN THE ONE OF SAIDCOMPARTMENTS FORMED BY SAID HOT JUNCTION SIDES BEING ADAPTED TO MELTPREVIOUSLY FROZEN, PURIFIED BODIES OF SAID FLUID MEDIUM DISPOSEDTHEREIN, AND MEANS FOR SELECTIVELY WITHDRAWING SAID PURIFIED FLUIDMEDIUM FROM SAID COMPARTMENTS IN THE FLUID STATE.